A common feature of many tumor viruses is that they possess genes that produce specific proteins to inhibit major cellular tumor-suppressor pathways. Despite intensive studies, the reasons why these diverse and unrelated viruses have independently evolved oncogenes remains obscure. Kaposi-sarcoma-associated herpesvirus (KSHV or HHV8) has pirated a number of recognizable cellular genes that are key to cell survival and proliferation. In this review, we provide an overview of the known activities of these viral genes and show that many of these pirated proteins affect the same cellular pathways targeted by other, unrelated tumor viruses. We speculate that tumor-suppressor pathways are used by the cell as a primary defense against persistent virus infection, in addition to their well-known activity in regulating cell proliferation.